Fluid-ejection devices, such as ink-jet print heads, usually include a die, e.g., formed on a wafer of silicon or the like using semi-conductor processing methods, such as photolithography or the like. A die normally includes resistors or piezoelectric elements for ejecting fluid, e.g., marking fluids, medicines, drugs, fuels, adhesives, etc., from the die, and a fluid-feed slot (or channel) that delivers the fluid to the resistors or piezoelectric elements so that the fluid covers the resistors or piezoelectric elements. Electrical signals are sent to the resistors or piezoelectric elements for energizing them. An energized resistor rapidly heats the fluid that covers it, causing the fluid to vaporize and be ejected through an orifice aligned with the resistor. An energized piezoelectric element expands to force the fluid that covers it through the orifice.
Traditionally, the fluid feed slot has been formed with an abrasive sand blast process. To facilitate the development of smaller parts, the fluid-feed slot in the wafer is now formed using an electromagnetic beam, such as a light or laser beam, which allows much greater dimensional control. Until recently, the fluid-feed slot was formed in the wafer using a laser beam, with a hydrofluorcarbon (HFC) assist gas. However, hydrofluorcarbon (HFC) assist gases are being phased out due to environmental concerns. For some fluid-feed slot formation processes, a water-assist process has replaced HFC assist processes. Some processes involve covering components formed on the wafer prior to forming the slot to protect them during the formation of the slot. However, such coatings are typically water-soluble and cause problems for the water-assist process.